Population & Samples

  • Population: A set of objects that are of interest
  • Census: An observation/measurement of every member of a population
  • Sample: A selection of observations/measurements of a subset of a population which is used to estimate information about the whole population
  • Sampling Units: Individual units of a population
  • Sampling Frame: Sampling units that are individually named/numbered to form a list

Sampling Methods

  • Simple Random Sampling: Every member of the population has equal chance of being selected
  • Systematic Sampling: Required elements are chosen at regular intervals from an ordered list
  • Stratified Sampling: The population is divided into mutually exclusive strata and a random sample is taken for each. The size of strata is proportional to its size compared to the whole population
  • Quota Sampling: An interviewer selects a sample that reflects the characteristics of the whole population
  • Opportunity/Convenience Sampling: Taking a sample from people who are available at the time and fit your given criteria